1. Field of the Invention
The present invention relates to a method and apparatus for fitting a mouth to a glass container, such as a beaker or teapot, that is, for molding a spout in the opening edge of a glass container.
2. Prior Art
The operation of molding the spout of a blow-molded glass container, such as a beaker, is effected by locally heating the upper opening edge of the glass container to soften it and pushing out the softened portion from the inside to the outside.
A conventional spout molding apparatus is arranged as shown in FIG. 8. The reference numeral 81 denotes a horizontally disposed, vertically movable lifting plate. A first air cylinder 82 for vertically moving the lifting plate 81 is suspended at a fixed position above the lifting plate 81, having a rod 83 fixed at its lower end to the lifting plate 81. The rod 85 of a second air cylinder 84 disposed on the upper surface of the lifting plate 81 extends downward through the lifting plate 81. The numeral 86 denotes a fixed link suspended from the lower surface of the lifting plate in parallel relation to the rod 85 of the second air cylinder 84, and 87 denotes a press link pivotally connected to the front end of the rod 85 of the second air cylinder 84 through a pivot shaft 88. The opposite ends of a connecting link 89 upwardly inclined toward the press link 87 are pivotally connected to the lower ends of the fixed link 86 and press link 87 through pivot shafts 90 and 91, respectively. A molding member 4 of inverted L-shaped cross section fixed to the lower surface of the connecting link 89 is adapted to push open that portion 1b of the upper opening edge 1a of a glass container 1 positioned on a stage 2 which is softened by being heated by a burner 3. That is, the rod 83 of the first air cylinder 82 is projected to lower the lifting plate 81 to position the downwardly inclined end 89a of the connecting link 89 at the upper surface opening 1d of the glass container 1. Subsequently, the rod 85 of the second air cylinder 84 is projected, whereby the press link 87 is turned outward around the axis of the pivot shaft 88, depressing the upwardly inclined end 89b of the connecting link 89. Thereupon, the connecting link 89 is turned downward around the axis of the pivot shaft 90, causing the molding member 4 to depress the softened portion 1b of the upper opening edge 1a of the glass container 1 so as to open it outward, so that as shown in phantom lines, a spout 1c having a forming angle .theta. is formed in the upper opening edge 1a of the glass container 1 (see FIG. 7C).
If the forming angle .theta. of the spout 1c of the glass container 1 is an obtuse angle, the drip-free quality of the spout 1c is poor; thus, in order to improve the drip-free quality, it is necessary that the forming angle .theta. of the spout 1c of the glass container 1 be a right angle (FIG. 7B) or an acute angle (FIG. 7A) smaller than that. However, according to a conventional spout molding apparatus, when a spout is to be molded, the softened portion 1b of the upper opening edge 1a of the glass container 1 is pressed from above by the molding member 4. Therefore, in the case of a right angle or an acute angle smaller than that, the deformation toward the outside is not smoothly effected, resulting in acquiring wrinkles on the molded surface of the spout 1c. This formation of wrinkles increases as the forming angle .theta. is made more acute in an effort to improve the drip-free quality. Thus, with the conventional spout molding apparatus it has been difficult to form a spout 1c whose forming angle is acute.
Further, since the length of the connecting link 89 and the stroke of the second air cylinder 84 in the conventional spout molding apparatus are constant, the forming angle .theta. of the spout 1c of the glass container 1 cannot be changed. Thus, in the case of molding spouts having different forming angles, spout molding devices corresponding to the different forming angles have to be provided, leading to increased cost and to increased time and labor involved in the exchange of devices, detracting from operability.
Further, since it is required that the spout have satisfactory drip-free quality and be prevented from acquiring wrinkles, as described above, care is taken in molding so that the shape is stabilized so as not to acquire wrinkles on the molded surface, but in some types of glass containers there are cases where it is difficult to mold a satisfactory spout. For example, as shown in FIGS. 9A and 9B, one case is of a glass container in the form of a bottomed cylindrical body having an inwardly inclined opening edge 1a in the upper region. FIG. 9A is a side view, partly broken away, of a glass container being locally heated, and FIG. 9B is a side view, partly broken away, of the glass container whose spout is being molded. The glass container 1 is positioned on a horizontal stage 2 and the spout molding scheduled portion of the opening edge 1a is locally heated by a burner 3 to soften said portion, and then the softened portion 1b of the opening edge 1a is pressed outward by a plate-like molding member 4 shown in phantom lines in FIG. 9B, thereby molding a spout 1c. The glass container 1 is intermittently transferred to positions including the heating position and the molding position as by a turntable. In the heating position, the opening edge 1a is heated and in the spout molding position, the locally heated softened portion 1b of the opening edge 1a is molded to form a spout. However, during the time that the glass container 1 is transferred from the heating position to the spout molding position, the locally heated softened portion 1b of the inclined opening edge 1a tends to sag under its own weight. The thus sagging softened portion 1b cannot be properly treated by the molding member 4, with the result that the molded spout 1c is disfigured and in the worst case it becomes impossible to mold the spout 1c. For this reason, it has been common practice in some cases to perform the local heating while holding the glass container 1 horizontal or oblique so as to prevent the softened portion 1b to be locally heated from sagging. However, in this case, the mechanism for transferring the glass container 1 while holding it horizontal or oblique becomes complicated, leading to an increase in the manufacturing equipment cost.